Year	Percent
1991	53.04
1992	52.95
1993	52.66
1994	52.56
1995	52.84
1996	53.04
1997	53.24
1998	53.43
1999	53.48
2000	53.46
2001	53.49
2002	53.24
2003	52.9
2004	52.62
2005	52.46
2006	52.52
2007	52.59
2008	52.56
2009	52.01
2010	51.56
2011	51.42
2012	51.22
2013	50.84
2014	50.5
2015	50.18
2016	50
2017	49.86
2018	49.63
2019	49.34